Osteoarthritis (OA) is a cartilage degenerative disease that leads to loss of proper function of the tissue. Early degeneration of OA cartilage is associated with the loss of proteoglycans (PG). We have recently shown that it is possible to measure PG loss in cartilage indirectly by quantitation of sodium by 23Na MRI of articular cartilage in-vivo and in-vitro. We want to further characterize this sodium by classifying it into two species based on their environments. In biological tissues there exists free and bound sodium fractions. The free sodium is usually in isotropic motion whereas bound sodium undergoes anisotropic motion and hence the 23Na NMR signal decay is biexponential in these tissues. We are attempting to precisely quantify the amount of bound sodium in phantoms and cartilage by 23Na Multiple Quantum Filtered (MQF) NMR. By measuring the equilibrium magnetization by both SQ and MQF signals will enable one to quantitate bond fraction of sodium. We ha ve measured this in phantoms and currently in the process of measuring in cartilage.